At least one type of font for displaying letters, numbers, or symbols (characters) corresponding to every language description desired by a user is required for document display using a computer. Usually, the characters to be displayed are specified by character codes, such as the ASCII or ANSI character codes. Thus to display the letter A, a code of 65, the ASCII code for the letter A, is sent to the display. The appearance of the displayed characters depends on the font in which the characters is displayed. Multiple fonts exist and can be used in a document. The word font as used in this disclosure is a character set unified by typeface and size. Typefaces such as Courier and Helvetica exist for the Roman alphabet used in the English language. These typefaces may be available in a variety of point sizes, such as 8pt., 10pt., 12pt, etc. Typefaces such as Mincho and Gothic exist for the Japanese language.
While mainframe computers or medium-sized computers such as desktop computers are usually provided with a broad selection of different fonts. However, memory size limitations in small-sized computers, such as portable computers, mean that only a few fonts can be provided. This is especially problematical in computers that operate in languages such as Japanese or Chinese in which the character set expressed in each font is composed of a very large number of characters. In such languages, a single font can occupy most of the available memory.
When a set of document data representing a document is transferred between computers, for example, between computers connected to a network, the number of data transferred is reduced by limiting the document data to the character codes of the characters constituting the document. However, since information about the fonts of the character is excluded from the document data, the document as displayed on the terminal that receives the document data (the receiving apparatus) will usually look different from the document as displayed on the terminal that transmitted the document data (the sending apparatus).
The problem just described can be eliminated by including font information in the document data. However, if the receiving apparatus is to display the document in the same fonts as those used to display the document on the sending apparatus, the receiving apparatus must be provided with a large memory to store a large variety of fonts. Small computers, such as portable computers, may lack the memory capacity for this.
In addition, there may be a chance that a document created on the sending apparatus includes special characters not normally used by the user of the receiving apparatus. For example, the document created on the sending apparatus may include characters of a language that is foreign to the user of the receiving apparatus. For example, the French character .cedilla., the German character a and the Spanish character n do not exist in the ASCII character set. In this case, the user of the receiving apparatus cannot completely display the document or can only display parts of the document unless the font or fonts provided in the receiving apparatus include the special characters. Naturally, a document can be completely reproduced by increasing the character set represented in each font, but this requires additional memory. Providing additional memory to store rarely-used special characters can be regarded as in inefficient use of such additional memory.
Instead of transferring document data composed of character codes between the computers connected to a network, the document can be transferred as a set of bitmaps, one bitmap for each character of the document. In this case, however, the number of data required to represent the document is much greater than the number of data required to represent the document using character codes. Therefore, when transferring documents as bitmaps, the transfer takes a long time and the user experiences a long delay between the start of the document transfer and the time when the document is finally displayed on the receiving apparatus. Moreover, the document transfer can consume a considerable fraction of the transmission bandwidth of the network, which slows other network traffic. Editing the document at the receiving apparatus is difficult because the characters that have been converted into bitmaps require character recognition software to convert the bitmaps back to character codes. Such software is complex and may be subject to recognition errors.
What is needed is a document display system capable of displaying a document in a receiving apparatus in the same font as that in which the document was displayed in the sending apparatus even if the fonts for displaying the characters forming the document are not provided at the receiving apparatus.
What is also needed is a document display system in which a document can be displayed on a receiving apparatus at high speed with a small amount of data transfer and that can display special characters without significantly reducing the display speed or increasing the amount of data transfer.